The assignee of the present invention is a manufacturer of apparatus for sorting parts and particularly for sorting bottle caps, known as "crowns". Devices to sort parts are generally known in the prior art. Typically, as the crowns enter a sorter, they move from a large chute to a rotating hopper bowl. From the hopper bowl, the crowns move into a twist chute which separates the crowns into face up and face down, and then twists one group, so that all the crowns are facing the same way when they exit the chute into a reservoir. The crowns then enter and move along a track, where defective crowns are located and discarded. The crowns remaining in the stream are accelerated to the speed required for the feed of the production line, using mechanical drive means and air. As the crowns exit the accelerator, they are received by a rotating wheel which includes recesses to receive the crowns. The rotating wheel feeds the crowns to the production line, which typically includes application of plastic liner material into the crowns.
The mechanical parts that move the crowns along the track for sorting defective crowns, and that accelerate the crowns, undergo great wear due to the high speed of the sorter device, particularly when metal crowns are sorted. A typical prior art device utilizes magnetic wheels with recesses for the crowns that resemble gears. The metal crowns are attracted to the wheel and slip into the recesses easily. Large numbers of metal crowns, with relatively sharp edges, are constantly ground against the gears, causing the pieces to wear quickly and need replacement. In addition, all of the drive components are subject to wear from the constant use at high speed.
It is desirable to sort the crowns at a constant high rate to insure accurate crown placement for the production line, but this has been difficult to achieve in prior art mechanisms. Using mechanical components and forced air to achieve the precise speed is also difficult because the crown feed speed cannot easily be changed to accommodate increases or decreases of the production line. U.S. Pat. No. 4,006,812 to Everett et al. discloses one type of automatic feeding hopper which uses mechanical means.
Another problem with crown sorting machines is blockages or jams caused by bent crowns becoming lodged in the machine. When a blockage occurs, crown flow is stopped until the bent crown is removed. This requires an operator to notice that the crown flow has stopped, and to turn off the machine so that the blockage can be located and manually removed. Most often these blockages occur at the inlet of the twist chute, where the crowns are feeding at a high rate, normally between 2000 and 3000 per minute.
An apparatus and method for detecting defective parts is disclosed in U.S. Pat. No. 4,879,025 to Shapcott. The disclosed apparatus sorts defective parts from a stream of parts through an inspection device that activates a reject disk when a defective part is detected. The reject disk then will rotate to remove the defective part. This apparatus is effective at detecting defective crowns and removing them, but it could not be used to prevent blockages that occur as the crowns exit the hopper bowl, because it requires the crowns to already be moving along a track. Thus, a need exists for an apparatus that can detect and remove defective crowns before they move along the track.